1. Field of the Invention
The invention relates to a light emitting apparatus and a display that, through the utilization of a light emitting device or an LED lamp as a light source, can be applied, for example, to on-vehicle lights or other lighting units, display units and the like.
In this specification, an LED chip per se is referred to as “light emitting device,” and the whole system including an LED chip-mounted package resin or lens system or other optical system is referred to as “light emitting diode,” “LED,” or “light emitting apparatus.”
2. Related Art
An increase in brightness of light emitting devices has led to extensive use of light emitting apparatuses using LEDs as a light source, for example, in backlights of automobiles. LEDs have a narrow-band emission spectrum, and the emitted light has good visibility. Further, the speed of response of LED is so high that the speed of transmission of signals to following vehicles is high and, thus, the distance necessary for stopping the travel of vehicles during high-speed traveling can be significantly reduced. LEDs per se are a monochromatic light source. Therefore, unlike incandescent lamps, there is no need to cut off light rays other than light of necessary color through a filter, and monochromatic light sources with a high emission efficiency can be realized. This also leads to energy saving.
An example of this type of conventional light emitting apparatuses is shown in FIG. 1. FIG. 1 is a cross-sectional view showing the whole construction of the conventional light emitting apparatus. As shown in FIG. 1, in this light emitting apparatus 100, a lenticular LED 101 produced by sealing a light emitting device 102 with a transparent epoxy resin 105 to form a package in a convex lens form is used as a light source. In the production of this lenticular LED 101, the light emitting device 102 is mounted on one lead 103a of a pair of leads 103a, 103b, the light emitting device 102 is bonded to the lead 103b by a wire 104, and the whole assembly is sealed with the transparent epoxy resin 105 to form the package in a convex lens form. The periphery of the lenticular LED 101 is covered with a reflecting mirror 106 in the form of paraboloid of revolution. A Fresnel lens 107 is provided in an upper central part of the lenticular LED 101. Light rays radiated from the lenticular LED 101 are reflected from the reflecting mirror 106 or are collected in the Fresnel lens 107 and exit upward substantially parallel to one another. The substantially parallel light rays are spread by a concave/convex interface provided on the lower surface of a resin lens 109. The light rays passed through the resin lens 109 are radiated, to the outside of the system, as emitted light having a spread angle of about 20 degrees which meets the specifications of on-vehicle backlights.
In these days, the output of the light emitting device is more and more increased, and this makes it necessary to cover a predetermined emission area using a minimized number of light emitting devices from the viewpoint of reducing the necessary number of components and reducing the time necessary for mounting the components. There is also a demand, for example, for an on-vehicle backlight of a new design, in which linear light emitting apparatuses are arrayed at predetermined intervals. In the above light emitting apparatus 100, an attempt to cover a further elongated area by one light emitting device results in the necessity of a longer size in the area direction, as well as in the necessity of an increased size in the thicknesswise direction. An excessive reduction in thickness deteriorates impressiveness of light rays emitted to the outside of the system. This poses a problem that a thin light source, which is a feature of the LED, cannot be produced. Further, light rays, which have been emitted from the light emitting device 102 but have reached neither the reflecting mirror 106 nor the Fresnel lens 107, cannot be optically controlled and thus cannot be radiated to the outside of the system. Thus, the conventional light emitting device still has room for improvement in external emission efficiency.